Disk recording device

ABSTRACT

For an overwriting operation, recorded data is read from a disk, and a bit clock is reproduced from the read, recorded data in a clock reproduction circuit ( 7 ). Data processing in an encoder ( 14 ) is performed in synchronism with the reproduced bit clock. With the above, recording data is output from the encoder ( 14 ) in synchronism with the recorded data in the disk whereby recording data to write onto the disk for overwriting is synchronized with the recorded data. A defined recording region is thus precisely overwritten.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an overwrite type disk recordingdevice which allows overwriting of data already recorded on a disk, andin particular to a disk recording device for data overwriting whileensuring synchronism between recorded data and overwritten recordingdata.

[0003] 2. Description of the Related Art

[0004] A CD-RW (compact disk rewritable) drive is a known type of CD(compact disk) disk recording device for data overwriting onto a disk.

[0005] In a CD-RW drive, a recording position is detected with referenceto a recorded address, referred to as ATIP (Absolute Time inPre-groove), which has been FM-modulated into a wobble of 22.05 kHz of apre-groove formed on a blank disk.

[0006] In a typical CD-RW, recording data to be recorded onto a disk anda sub-code contained in recording data are synchronism with asynchronous signal of an ATIP.

[0007] Synchronism between a synchronous signal of an ATIP and that of asub-code, however, may be impaired due to irregular disk turning and soon, even though a resultant displacement between the synchronous signalsis tolerable within a predetermined range.

[0008] In particular, with a CD-RW drive capable of high speed writing,such displacement is likely to occur as acceleration or decelerationtorque of a spindle motor are more likely to be shorted.

[0009] In recording a signal onto a disk while referring to an ATIP,such a displacement in synchronism between synchronous signals of anATIP and of a sub-code would hinder establishment of synchronism betweenalready recorded data and overwriting recording data.

[0010] In general, overwriting in a packet-writing method does notrequire synchronism established between recorded data and overwritingrecording data. However, as all CD-ROM drives may not be able to employthe packet-write method, a track-at-once method or a session-at-oncemethod may be preferred for data recording in view of compatibility witha CD-ROM drive.

[0011] In addition, a packet-writing method requires as many as sevenlink blocks to be formed for packet connection, and thus may waste diskstorage capacity.

[0012] In view of the above, for data overwriting onto a disk, a methodfor data-writing without leaving a trace of rewriting would be preferredif that would be possible, in view of compatibility with a CD-ROM andeffective utilization of disk storage capacity. Thus, a disk recordingdevice capable of data overwriting while leaving no trace, or only asubtle trace, of rewriting is desired.

[0013] For data rewriting while leaving no or a subtle trace,overwriting of recording data must have precise synchronism with thedata then recorded on the disk. Otherwise, the newly recorded data mightbe written beyond a defined recording region, which may cause problemsof partial damaging of recorded data beyond the region, or incompletewriting of a prescribed amount of overwriting recording data with partlycut-off toward the end thereof.

SUMMARY OF THE INVENTION

[0014] The present invention is directed to achieving precise writing ofrecording data to overwrite corresponding recorded data on a disk withina defined recording region while ensuring synchronism between therecording and recorded data.

[0015] According to the present invention, in data overwriting, recordeddata is read from a disk, and a bit clock is reproduced from the readrecorded data in a clock reproduction circuit so that data is processedin an encoder in synchronism with the reproduced bit clock. Recordingdata is accordingly output from the encoder in synchronism with the datarecorded in the disk thereby synchronizing the overwriting recordingdata with the recorded data.

[0016] With this arrangement, in which recording data is output from anencoder in synchronism with the recorded data in a disk and written foroverwriting the disk in synchronism with the recorded data, theoverwriting data can be written precisely within a defined recordingregion. This can prevent problems such as partial damaging of therecorded data due to overwriting beyond a defined recording region, orincomplete writing of a prescribed amount of overwriting data.

[0017] Consequently, overwriting recording data can be written onto adisk while leaving no trace, or only a subtle trace, of rewriting on thedisk in a boundary, and the overwriting data written on the disk can bereproduced successive to the preceding recorded data to help ensurecompatibility with a typical CD-ROM drive.

[0018] Further, a bit clock can be readily reproduced even during anoverwriting operation, when the bit clock is reproduced from therecorded data read by a preceding beam prior to a main beam.

[0019] Still further, a constant output can be maintained with thepreceding beam even during a recording operation using a main beam whenthe preceding beam is emitted from a second light source, which isdifferent from a light source emitting the main beam. This ensuresreliable reproduction of a bit clock.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features, and advantages of thepresent invention will become further apparent from the followingdescription of the preferred embodiment taken in conjunction with theaccompanying drawings wherein:

[0021]FIG. 1 is a block diagram showing a preferred embodiment of a diskrecording device according to the present invention in the form of aCD-RW drive; and

[0022]FIG. 2 is a diagram illustrating irradiation state on a signaltrack of a compact disk by respective light beams from an optical head,and light receiving elements of a light detector for receivingreflection beams of the respective light beams.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023]FIG. 1 is a block diagram showing a preferred embodiment of a diskrecording device according to the present invention in the form of aCD-RW drive.

[0024] The drawing shows an optical head 1 for emitting a laser beam fortracing a signal track on a compact disk so that recording data iswritten on or recorded data is read from a disk.

[0025] The optical head 1 has two light sources, one forming a main beamand the other forming a beam to be split through diffraction into two,namely a preceding beam arranged before the main beam and a followingbeam arranged behind the main beam.

[0026] This arrangement advantageously prevents diffraction of the mainbeam, and allows the power of the preceding and following beams to beset independently of that of the main beam so as to be free from theinfluence of variances in the power of the main beam.

[0027] The main, preceding, and following beams irradiate separateportions of a same signal track T, respectively forming a light spot S0(main beam), a light spot S1 (preceding beam), and a light spot S2(following beam), as shown in FIG. 2. A reflection beam of the mainbeam, reflected from the disk, is received by a first light receivingelement, which is divided into two light receiving regions 1 a, 1 b, ofa light detector provided to the optical head 1. A reflection beam ofthe preceding beam, reflected from the disk, is received by a secondlight receiving element 1 c of the light detector. A reflection beam ofthe following beam, reflected from the disk, is received by a thirdlight receiving element 1 d of the light detector.

[0028] A first RF amplifier 2 performs addition or subtractionoperation, as well as amplification, using an RF signal (a radiofrequency signal) of received light outputs Sa, Sb from the respectivelight receiving regions 1 a, 1 b of the first light receiving element,and binarizes an addition or subtraction signal obtained throughaddition or subtraction to produce a resultant signal which it outputs.A second RF amplifier 2 amplifies a received light output Sc from thesecond light receiving element 1 c, binarizes the RF signal, and outputsthe resulting data. The third RF amplifier 3 similarly processes a lightSd received from the third light receiving element 1 d. A head servocircuit 5 performs focusing control, tracking control, and thread feedcontrol based on feedback of an output of the optical head 1 via thefirst RF amplifier 2. Through focusing control, the laser beam isfocused on a signal plane and, through tracking control, the laser beamtracks the signal track of the disk. Through thread feeding control, theoptical head 1 is moved in the radial direction of the disk.

[0029] A selection switch 6 can be switched for a state, when reading,for selecting a binary data (EFM data) binarized from an addition signalobtained by the first RF amplifier 2, and also for a state, whenrecording, for selecting binary data (EFM data) binarized by the secondRF amplifier 3. A clock reproduction circuit 7 reproduces a bit clockfrom the data selected by the selection switch 6. A decoder 8demodulates data on an addition signal from the first RF amplifier 2 insynchronism with a bit clock reproduced by the clock reproductioncircuit 7. A sub-code demodulation circuit 9 separates a sub-code fromEFM data output from the first RF amplifier 2, and demodulates theseparated sub-code.

[0030] A wobble decoder 10 demodulates data on a subtraction signal fromthe first RF amplifier 2 to thereby extract 22.05 kHz wobble componentsfrom a pre-groove signal from the disk to generate components necessaryfor disk turning control. The wobble decoder 10 includes an ATIPdemodulation circuit 11 for demodulating wobble components to restore anATIP (absolute time in pre-groove).

[0031] An interface 12 controls data transmission with respect to a hostdevice, such as a personal computer, which is externally connected via aconnection terminal 13. An encoder 14 modulates data received via theinterface 12 into recording data to be recorded onto a disk. A bufferRAM 15 is used for caching data received via the interface 12 and usedwhen the cached data is modulated in the encoder 14 into recording datato be recorded onto a disk. Furthermore, the buffer RAM 15 is used forcaching data read from the disk, and used when the data is demodulatedin the decoder 8.

[0032] The encoder 14 has a CD-ROM modulator for modulation based onCD-ROM standard, and a CD modulator for modulation based on CD-DAstandard. The CD-ROM modulator imparts synchronization (sync), header,EDC (error detection code), and ECC (error correction code) to receivingdata, EDC being an error detection code for CD-ROM data, and ECC beingan error correction code for CD-ROM data. The CD modulator performs CIRC(cross interleaved reed-solomon code) processing and imparts a sub-codeto data output from the CD-ROM modulator, CIRC being an error correctioncode in a CD method. The CD modulator also performs EFM (eight tofourteen modulation) and imparts a synchronous signal.

[0033] A laser driving circuit 16 drives a laser source of the opticalhead 1 to record onto a disk based on recording data in the form of EFMdata from the encoder 14. A verifying circuit 17 compares recording datafrom the encoder 14 and EFM data from the third RF amplifier 4 throughtime adjustment for time conformity to thereby verify recorded datawritten on a disk.

[0034] A system control circuit 18 is responsible for system control inconnection with data recording onto and reproduction from a disk, andcomprises an access control means 19, a buffer control means 20, arecording control means 21, a recording start position detection means22, and a synchronism establishment means 23. The access control means19 controls access to the disk with selective reference to a sub-codeaddress expressed in the form of absolute time information contained ina sub-code (sub-Q-code), which is demodulated in the sub-codedemodulation circuit 9, and an ATIP address expressed in the form ofabsolute time information contained in an ATIP, which is demodulated inthe ATIP demodulation circuit 11. The buffer control means 20 controlsdata writing and reading with respect to the buffer RAM 15. Therecording control means 21 controls data recording onto a disk accordingto the amount of data stored in the buffer RAM 15, which is controlledby the buffer control means 20. The recording start position detectionmeans 22 detects a recording start position at which the recordingcontrol means 21 starts data recording. The synchronism establishmentmeans 23 synchronizes recording data to be newly recorded onto a diskwith recorded data existing on the disk, using a synchronous signal of asub-code extracted by the decoder 4 and sub-Q-data demodulated by thesub-code demodulation circuit 9.

[0035] The thus constructed disk recording device executes a recordingoperation upon receipt, via the interface 12, of data with a request forbeing recorded onto a disk.

[0036] When a not-recorded region on a disk is designated as a recordingregion and a data recording operation thereonto is started, a systemclock of the recording circuit is used as a reference clock with crystaloscillation accuracy, and data processing in the encoder 14 is performedin synchronism with a reference clock.

[0037] The optical head 1 is controlled so as to read a pre-groovesignal from a disk, using a main beam, a laser output for disk reading.The read pre-groove signal is supplied to the first RF amplifier 2 forwaveform shaping, and then to the wobble decoder 10 for extraction ofwobble components. The extracted wobble components are demodulated intoan ATIP in the ATIP demodulation circuit 11.

[0038] When an external device sends data with a recording request via aconnected connection terminal 13, the data is received by the interface12 and then written into the buffer RAM 15.

[0039] Data is received by the interface 12 in block units. When apredetermined number of data blocks have been written into the bufferRAM 15, that number being a recording unit set in advance, the data istogether modulated in the encoder 14 into recording data in the formsuitable for data recording.

[0040] Meanwhile, when the main beam of the optical head 1 tracing thedisk reaches a point at which data writing is to start, the encoder 14begins sequential output of recording data in the EFM frame unit.Moreover, address data on the address corresponding to the outputrecording data is sequentially updated and stored in the address memory24 in the system control circuit 18.

[0041] Based on the recording data from the encoder 14, the laserdriving circuit 16 drives the laser source of the optical head 1 tothereby write recording data onto the disk.

[0042] Next, operation for overwriting a disk with recording data willbe described.

[0043] When data with an overwrite request is received from a hostdevice via the interface 12, the recording start position detectionmeans 22 initiates detection of a recording start position on a disk. Anoverwrite request from a host device includes a designation of arecording region to be overwritten, the designation containing data on astart address of the recording region, data length of overwriting data,and the like.

[0044] Upon initiation of detection by the recording start positiondetection means 22, the access control means 19 accesses an address on adisk which precedes by a predetermined amount the start address of therecording region designated in the overwrite request with reference toan ATIP, which is demodulated in the ATIP demodulation circuit 11.

[0045] When access is completed, the optical head 1 begins tracing thedisk to read a pit signal from the disk using the main beam.Accordingly, EFM data is obtained from the first RF amplifier 2.

[0046] The EFM data from the first RF amplifier 2 is supplied to thedecoder 8. The decoder then extracts a synchronous signal of a sub-codefrom the EFM data, and the sub-code demodulation circuit 9 demodulatesthe EFM data into a sub-Q-code.

[0047] The resultant sub-Q-code is used for detection of a recordingstart position by the recording start position detection means 22. Thatis, detection of a recording start position in sub-code frame units (acollection of 98 units of EFM frames) is made through access tosub-Q-data.

[0048] The extracted synchronous signal of a sub-code is used forestablishment of synchronism by the synchronism establishment means 23to synchronize recording of data to be newly recorded onto a disk withrecorded data already stored on that disk.

[0049] After determination of a recording start position in a sub-codeframe unit, a recording start position in an EFM frame unit is thendetermined by counting a channel bit using a synchronous signal as areference. In this manner, a recording start position is determined.

[0050] During a process to determine a recording start position in arecording region for overwriting as described above, data with arecording request is received via the interface 12. When a predeterminednumber of blocks of such data has been written into the buffer RAM 15,the encoder 14 resumes modulation processing to thereby resumepreparation of recording data.

[0051] When a recording start position is determined, the encoder 14outputs recording data, which triggers a writing operation using therecording data to overwrite the disk.

[0052] For overwriting, the selection switch 6 is switched as shown bythe solid line in FIG. 1, in which state clock reproduction circuit 7reproduces a bit clock from EFM data from the second RF amplifier 3.

[0053] The second RF amplifier 3 then receives a received light outputSc from the second light receiving region 1C, which receives reflectionlight of the preceding beam from the optical head 1, and an EFM signalcorresponding to a pit signal read by the preceding beam is output fromthe second RF amplifier 3.

[0054] As the preceding beam is emitted from a light source differentfrom that of the main beam, which is arranged to alternatingly output arecording power and an erasing power during data recording onto a disk,constant reproduction power of the preceding beam can be maintainedduring a recording operation. This enables reliable reproduction of abit clock by the clock reproduction circuit 7.

[0055] Specifically, even during a process of overwriting a disk withrecording data using a main beam, the clock reproduction circuit 7 canreproduce a bit clock based on the recorded data written in the disk ata point immediately before the very point where recording data is beingwritten.

[0056] The thus reproduced bit clock is used as an operation clock forthe decoder 8 and the encoder 14 so that demodulation and modulationoperations are carried out by the decoder 8 and the encoder 14,respectively, in synchronism with the bit clock.

[0057] Therefore, the encoder 14 outputs recording data in synchronismwith the bit clock, so that recording data is written onto the disk insynchronism with the recorded data. This enables precise overwriting ina defined recording region, and, as a result, recording data can bewritten onto the disk while leaving no trace, or only a very subtletrace, of rewriting in a boundary from the recorded data. Consequently,the recorded data in the overwritten recording region can be reproducedsuccessive to the preceding recorded data, which helps to establishcompatibility with a typical CD-ROM drive.

[0058] Here, during a recording operation using recording data ontodisk, an EFM signal from the third RF amplifier 4 is supplied to theverifying circuit 17. The verifying circuit 17 delays the recording data(EFM data) from the encoder 14 for time conformity, and compares therecording data with an EFM signal from the third RF amplifier 4.

[0059] As the third RF amplifier 4 then receives a received light outputSd from the third light receiving region id, which receives a reflectionlight of the following beam of the optical head 1, an EFM signalcorresponding to a pit signal read by the following beam is output fromthe third RF amplifier 4. Therefore, the third RF amplifier 4 outputs anEFM signal corresponding to the recording data just recorded onto thedisk.

[0060] As described above, recording data being just recorded onto thedisk is verified in the verifying circuit 17.

[0061] It should be noted that, as the main beam is arranged toalternatingly output a recording power and an erasing power during awriting operation onto a disk using recording data, reproduction of abit clock directly from a received light of the main beam would bedifficult. However, reproduction of a bit clock based on a differenceobtained by subtracting a varying amount of the main beam output fromthe received light output of the main beam would be possible. In thiscase, the preceding beam is unnecessary, and the number of light sourcesof the optical head 1 can be reduced to one when the following beam isformed through diffraction of the main beam.

What is claimed is:
 1. A disk recording device capable of data writingonto a disk for overwriting, comprising: a clock reproduction circuitfor reproducing a bit clock from recorded data read from the disk; anencoder for data processing to modulate input data into recording datasuitable for recording onto the disk; and an optical head for readingrecorded data from the disk, and for writing the recording data suppliedfrom the encoder; wherein, for an overwriting operation, the opticalhead reads the recorded data from the disk, the clock reproductioncircuits reproduces a bit clock from the recorded data read by theoptical head, the encoder performs data processing in synchronism withthe bit clock reproduced by the clock reproduction circuit to therebyprepare recording data which is in synchronism with the recorded data,and the optical head writes the recording data onto the disk based on anoutput from the encoder.
 2. A device according to claim 1, furthercomprising an interface for receiving an overwrite request whichcontains a designation of a recording region to be overwritten with therecording data, and a recording start position detector for detecting arecording start position on the disk based on the designation of arecording region, which is contained in the overwrite request receivedby the interface, wherein recording of an output from the encoder whichis in synchronism with the bit clock reproduced by the clockreproduction circuit is begun at the recording start position detectedby the recording start position detector.
 3. A device according to claim1, wherein the optical head generates a main beam for recording onto thedisk, and a preceding beam for tracing a signal track on the disk priorto the main beam, and detects a reflection beam of the preceding beam,reflected from the disk, and the clock reproduction circuit reproducesthe bit clock based on a result of detection of the reflection beam ofthe preceding beam.
 4. A device according to claim 3, wherein theoptical head includes a first light source for generating the main beamand a second light source which is different from the first lightsource, for generating the preceding beam.
 5. A device according toclaim 4, wherein an output from the second light source is controlledindependently of an output from the first light source.
 6. A deviceaccording to claim 3, wherein the optical head generates a followingbeam for tracing the signal track on the disk subsequently to the mainbeam to detect a reflection beam of the following beam, reflected fromthe disk, and the disk recording device includes a verifying circuit forverifying data recorded on the disk by comparing a result of detectionof the reflection beam of the following beam and the recording datarecorded onto the disk by the main beam.
 7. A device according to claim6, wherein the optical head includes a first light source and a secondlight source which is different from the first light source, wherein themain beam is emitted from the first light source, and the preceding beamand the following beam are formed by splitting a beam emitted by thesecond light source.
 8. A device according to claim 1, wherein theoptical head generates a main beam for writing the recording data ontothe disk, and receives a reflection of the main beam, reflected from thedisk, and the clock reproduction circuit subtracts a varying amount ofan output of the main beam from a detection of the reflection of themain beam, reflected from the disk, and reproduces a bit clock based ona difference obtained by this subtraction.